a1 Materials Science and Engineering Department, University of Wisconsin, Madison, Wisconsin 53706
a2 Materials Science Program, University of Wisconsin, Madison, Wisconsin, 53706
a3 Materials Science and Engineering Department and Materials Science Program, University of Wisconsin, Madison, Wisconsin 53706
a4 Recording Head Operations, Seagate Technology, Bloomington, Minnesota 55435
For an interface to be considered thermodynamically stable, the phases in contact must be in equilibrium with each other (connected by a stable tie-line) and have negligible mutual solubility on the phase diagram. The stability of Co based magnetic tunnel junctions (MTJs), with Co/MxO1-x/Co structures (M = Al, Gd, Hf, La, Mg, Si, Ti, Ta, Y and Zr), were evaluated with regard to these two conditions. Specifically, low temperature ternary isothermal phase diagrams were calculated and evaluated for the Co–M–O systems. All of these systems have at least one oxide in equilibrium with Co and thus have at least one thermodynamically stable tunnel barrier candidate for use in Co based MTJs. In light of the assumptions made in this analysis, along with the uncertainty in applying bulk enthalpy data to thin films, the current evaluation of interfacial stability serves as a first step in identifying suitable stable tunneling barrier materials in MTJs for detailed study.
(Received June 24 2003)
(Accepted January 07 2004)